Google Product Forums
Re: Video not displaying (black, green, white box) but hear audio? Look here...
yeahknow Feb 16, 2011 11:11 PM
Posted in group: YouTube
) Black screen.  No audio.
2) Mac OS X 10.6.4
3) Safari 5.0.3

What the heck is the problem?  I called apple support and they were baffled - can you guyns help?  Virus?